Propellant with polymer containing nitramine moieties as binder

ABSTRACT

A novel binder for propellant compositions, and its method of preparation, said binder being a polymer of the formula:   and novel propellant compositions thereof.

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ttes atet 1 Comfort et al.

1 July 29, 1975 The United States of America as represented by theSecretary of the Navy, Washington, DC.

Filed: Jan. 21, 1974 Appl. No.: 435,073

Related U.S. Application Data Division of Ser. No. 219,183, Jan. 19,1972, Pat. No. 3,808,276.

Assignee:

U.S. Cl. 149/19.4; 149/19.6; l49/l9.8; 149/20; 149/92; 149/96; 149/97Int. Cl. C06D 5/06 Field of Search 149/96, 97, 92, 20, 19.6, l49/l9.4,19.8

References Cited UNITED STATES PATENTS 2/1964 Gey et a1. 149/92 X3,151,164 9/1964 Sammons 149/92 X 3,609,115 9/1971 Sammons et al....149/92 X 3,711,344 1/1973 Pierce 149/19.8 3,726,729 4/1973 Pierce149/19.8 3,756,874 9/1973 Chang ct al l49/l9.4 3,793,099 2/1974 Duerksenet a1 l49/19.4

Primary Examiner-Benjamin R. Padgett Assistant Examiner-E. A. MillerAttorney, Agent, or FirmR. S. Sciascia; .l. A. Cooke 5 7 ABSTRACT Anovel binder for propellant compositions, and its method of preparation,said binder being a polymer of the formula:

H (001,1 1 cH,cH,1 1 c11 0 ctnci-nipn.

and novel propellant compositions thereof.

13 Claims, No Drawings PROPELLANT WITH POLYMER CONTAINING NITRAMINEMOIETIES AS BINDER This is a division of application Ser. No. 219,183,filed Jan. 19, 1972, now US. Pat. No. 3,808,276.

BACKGROUND OF THE INVENTION Solid propellants are usually made of thethree basic ingredients: (1) oxidizer, (2) fuel, and (3) binder. Two oreven three of these may be contained in the same material. A convenientway to divide solid propellants into classes is according to physicalstate, i.e., homogeneous (single-base or double-base) and composite. Asingle-base propellant contains nitrocellulose as the main ingredientwith a stabilizer such as diphenylamine added, as well as otherconventional additives depending on the application. Single-basepropellants are used primarily in gun applications andcartridge-actuated devices. Double-base propellants have two principalingredients nitrocellulose and nitroglycerine, and may have variousconventional ingredients as stabilizers, burning rate modifiers,extrusion lubricants and flash suppressors. When additional oxidizersare added to the double-base propellant, one has a composite modifieddouble-base propellant. Composite propellants are generally composed ofan oxidizer and a fuel and/or binder. Well-known oxidizers and fuels areused.

The binder material in composite propellants usually is a polymericmaterial and nitrocellulose is the most commonly known and used bindercomponent. Thus, nitrocellulose finds wide use in all types ofpropellant formulations. However, the use of nitrocellulose as a binderin gun propellants results in a high flame temperature and low gasoutput, both of which are undesirable features. While the replacement ofnitrocellulose in gun propellants with a rubber binder gives betterflame temperature and gas output, it requires large amounts of outputfor efficient propellant combustion. Moreover, in solid rocketpropellants and other composite propellants, while nitrocellulose offershigh energy it generally gives poor low temperature mechanicalproperties and relatively high sensitivity. The use of a rubber binderfor these composite propellants improves the low temperature mechanicalproperties and sensitivity but such propellants are less energetic andless efficient than those based on nitrocellulose.

SUMMARY OF THE INVENTION It is an object of this invention to obtain anew binder for propellant compositions, and a method of preparing such abinder.

It is an additional object of the instant invention to obtain a newbinder for propellant compositions which has a low flame temperature.

It is a further object of the present invention to obtain a new binderfor propellant compositions with a high gas output.

It is still another object of the instant invention to producepropellant compositions which have good low temperature mechanicalproperties.

It is yet another object of the instant invention to produce apropellant having low sensitivity.

It is still another object of the invention to produce a binder forpropellant compositions which is thermally stable.

Still another object of the instant invention is to produce a binder forpropellant compositions which is compatible with other propellantingredients.

It is an additional object of the present invention to produce a binderfor propellant compositions which can be used as a replacement for oradditive to a nitrocellulose binder.

These and other objects are accomplished by the use of a new polymerbinder which offers the desirable advantages of both nitrocellulose andrubber binders, in solid propellants such as gun propellants and rocketpropellants.

The objects, advantages, and novel features of the invention will becomeapparent from the following detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The novel binderpolymer of the instant invention is a-hydro-w-hydroxy poly(oxymethylenenitramino),

and is designated as EDNAP. While any molecular weight polymer willsuffice so long as the polymer is operable for binder purposes, it ispreferred to use a polymer of a molecular weight of from about 750 toabout 3,000, or more preferably from about 1,000 to about 2,500. Thistype of polymer is synthesized by reactingl,6-dichloro-2,5-dinitrazahexane (DCDNH) with a polyhydroxy alcohol,exemplified by ethylene glycol. The polymer is thermally stable and canbe crosslinked with hexane diisocyanate to form a rubbery gumstock.

A more detailed description of the preparation is as follows. The DCDNH,which reacts with the polyfunctional alcohol, is prepared by reactingethylene dinitramine with formaldehyde and hydrogen chloride in aceticacid at about 0 C. The DCDNH is usually recrystallized from benzenebefore preparing the polymer. The bulk reaction between DCDNH and thepolyol may be carried out between room temperature and C., but the rangeof 4060 C. is preferred. The ratio of hydroxyls to chlorines in therespective reactants may be 1.0 to 1.3. Operation under reduced pressureis desirable so as to rapidly remove the hydrogen chloride generated bythe reaction and thereby prevent its reaction with the poly-ol. Prior touse in propellant formulations, the prepolymer should be thoroughlywashed with base.

EDNAP, when crosslinked, will form a high energy, low glass transitiontemperature binder which is nearly oxygen balanced and will form lowmolecular weight products upon combustion. The properties of EDNAP arecompared to nitrocellulose and butarez II (a rubber binder) in Table I,below.

Table l-Continued Nitrocellulose Butarcz EDNAP (12.67:) 11

Flame Tcmp. 1.800 3.435

(K) Gas Output 5.4 4.0

mo1es/l00,gms Density. gm/cc 1.36 1.66 0.90

Butare1 is not a monopropcllant The low flame temperature and high gasoutput of EDNAP is ideal for gun propellant applications. For example,propellants with about 20 percent EDNAP as a binder with otherwell-characterized compounds have a calculated impetus of up to 420,000ft-lb/lb at 2,70 OK. This is a 25 percent gain over Olin ball powderwhich is presently used for many gun propellant applications.

1n solid rocket propellants EDNAP also calculates well. For example,Table 11 shows two formulations which are comparable to compositemodified doublebase (CMDB) propellants in impulse. The advantages of theEDNAP binder rocket propellants are their expected good low temperaturemechanical properties and lower sensitivity compared to the CMDBpropellants.

"In use in solid propellants, the cured polymer is generally used. Thepolymer can be cured with any conventional curing agent such as any ofthe crosslinking polyfunctional isocyanates. Exemplary are toluenediisocyanate and hexan'e diisocyanate, to name just a few of the manyconventional crosslinking agents readily available. A wide variety ofpropellant compositions can be made using the cured prepolymer as thebinder. It is preferred to use the EDNAP in double-base and compositetype propellants, rather than in single-base propellants. In a compositepropellant the amount of EDNAP present is about 10 25 percent by weightof the propellant composition. In these composite types, conventionalfuels, such as aluminum, beryllium, zirconium, magnesium, boron, andtheir corresponding hydrides, as well as lithium, and lithium aluminumhydride, may be used in amounts varying from to 25 percent by weight,preferably at least about percent by weight. Conventional oxidizers,such as cyclotetramethylenetetranitramine (RDX), and ammonium and alkalimetal nitrates or perchlorates may be present in amounts ranging fromabout 55 to 90 percent. With respect to the latter, it would bepreferable to have from 55 to 80 percent of oxidizer because it isdesired to have at least 10 percent of fuel present in the composition,although the propellants would be operative in the absence of the fuels.In addition to the oxidizer, EDNAP and fuel, any of the conventionaladditives such as plasticizers, curing agents, stabilizers, burning rateadditives, catalysts, etc., are also possible components of thecomposite formulation The amount of curing agent necessary to crosslinkthe polymer is not critical and generally conventional amounts of about1 to about 6 percent will suffice. With respect to the amount ofplasticizer present, usually the EDNAP may be plasticized with up totwice its weight with energetic materials like nitroglycerine ordiethylene glycol dinitrate.

In a double-base type propellant, a satisfactory propellant can beobtained by replacing up to about one half of the nitrocellulose withEDNAP. Thus, while the typical double-base propellant will contain about30-50 percent by weight of a high energy explosive such asnitroglycerin, diethylene glycol dinitrate, methyl trimethylolmethanetrinitrate or others, and about 40 to about 60 percent ofnitrocellulose, the propellant compositions of the instant inventionwill con tain from about 1 to about 30 percent of EDNAP, replacing up toabout one half of said nitrocellulose, usu' ally present inthe'conventional type. The resulting propellant will have the polymerpresent in an amount equal to or less than the amount of nitrocellulosepres ent. Conventional additives, such as plasticizers (pthalates,triacetin, etc.), stabilizers (2 -nitrodiphenylamine, tertiary butylcatechol, etc.), burning rate modifiers (lead salts, etc.), extrusionlubricants (stearates, soaps, etc.), and flash suppressors (potassiumsalts, etc.) may also be added. g

The following examples illustrate the method of obtaining the novelpolymer as well as some propellant formulations utilizing the novelpolymer.

EXAMPLE I 0.6 moles of DCDNI-I, 0.56 moles of ethylene glycol, and 0.1 1moles of glycerol were reacted at 5060 C. for 24 hours at the lowpressure level produced by a water aspirator. The cooled reactionmixture was dissolved in methylene chloride and washed successively withwater, sodium bicarbonate solution, and finally sodium hydroxidesolution. For drying, benzene was added to the solution and the totalsolvent was distilled. Last traces of solvent were removed by spargingwith dry nitrogen at 60 C. The product, on analysis, was found tocontain 0.19 percent water and to have an hydroxyl equivalent weight of572.

EXAMPLE II A propellant formulation was prepared in the laboratory ofthe following composition:

This composition has a calculated specific impulse of 265 seconds and adensity of 0.065 lbs/in Its burning rate at 1,000 psi was 0.21 in/sec. 1

EXAMPLES Il1lV The two formulations set forth at Table I1, supra, areadditional examples of propellant compositions in which EDNAP isincorporated.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

l. A solid propellant composition which contains a cured polymer as abinder component therefor, said polymer being of the formula:

2. The solid propellant composition of claim 1, wherein said compositionis a composite type solid propellant comprising a propellant oxidizerand said polymer.

3. The composite type solid propellant of claim 2 comprising anoxidizer, a fuel, and said polymer.

4. The composite type solid propellant of claim 3 comprising from about55-80 percent by weight of said oxidizer, from about to about percent byweight of said fuel, and from about 10 to about 25 percent by weight ofsaid polymer.

5. The composite type propellant of claim 4 comprising 12 percent ofaluminum, 65 percent of HMX oxidizer and 19.2 percent of said polymer.

6. The composite type propellant of claim 4 comprising 25 percent ofsaid polymer, 50 percent of ammonium perchlorate oxidizer, and 25percent of aluminum fuel.

7. The composite type propellant of claim 4 comprising 20 percent ofsaid polymer, 15 percent of aluminum fuel, and 65 percent of HMXoxidizer.

8. The composite type polymer of claim 4 wherein said polymer is curedwith a difunctional isocyanate.

9. The composite type polymer of claim 4 wherein the molecular weight ofsaid polymer varies from about 750 to about 3,000.

10. A solid propellant composition according to claim 1 wherein saidcomposition is a double-base type propellant containing said polymer,nitrocellulose, and a high energy explosive selected from the groupconsisting of nitroglycerin, diethylene glycol dinitrate, and methyltrimethylolmethane trinitrate.

11. The double-base type propellant of claim 10 comprising from about 30to about 50 percent by weight of said high energy explosive, from about10 to about 59 percent by weight of nitrocellulose and from about 1 toabout 30 percent by weight of said polymer such that the amount of saidpolymer is equal to or less than the amount of nitrocellulose present.

12. The composite type composition of claim 11 wherein said polymer iscured with a difunctional isocyanate.

13. The composite type composition of claim 11 wherein the molecularweight of said polymer varies from about L000 to about 2,500.

1. A SOLID PROPELLANT COMPOSITION WHICH CONTAINS A CURED POLYMER AS ABINDER COMPONENT THEREFOR, SAID POLYMER BEING OF THE FORMULA:
 2. Thesolid propellant composition of claim 1, wherein said composition is acomposite type solid propellant comprising a propellant oxidizer andsaid polymer.
 3. The composite type solid propellant of claim 2comprising an oxidizer, a fuel, and said polymer.
 4. The composite typesolid propellant of claim 3 comprising from about 55-80 percent byweight of said oxidizer, from about 10 to about 25 percent by weight ofsaid fuel, and from about 10 to about 25 percent by weight of saidpolymer.
 5. The composite type propellant of claim 4 comprising 12percent of aluminum, 65 percent of HMX oxidizer and 19.2 percent of saidpolymer.
 6. The composite type propellant of claim 4 comprising 25percent of said polymer, 50 percent of ammonium perchlorate oxidizer,and 25 percent of aluminum fuel.
 7. The composite type propellant ofclaim 4 comprising 20 percent of said polymer, 15 percent of aluminumfuel, and 65 percent of HMX oxidizer.
 8. The composite type polymer ofclaim 4 wherein said polymer is cured with a difunctional isocyanate. 9.The composite type polymer of claim 4 wherein the molecular weight ofsaid polymer varies from about 750 to about 3,000.
 10. A solidpropellant composition according to claim 1 wherein said composition isa double-base type propellant containing said polymer, nitrocellulose,and a high energy explosive selected from the group consisting ofnitroglycerin, diethylene glycol dinitrate, and methyltrimethylolmethane trinitrate.
 11. The double-base type propellant ofclaim 10 comprising from about 30 to about 50 percent by weight of saidhigh energy explosive, from about 10 to about 59 percent by weight ofnitrocelluLose and from about 1 to about 30 percent by weight of saidpolymer such that the amount of said polymer is equal to or less thanthe amount of nitrocellulose present.
 12. The composite type compositionof claim 11 wherein said polymer is cured with a difunctionalisocyanate.
 13. The composite type composition of claim 11 wherein themolecular weight of said polymer varies from about 1,000 to about 2,500.